Searching for life on Mars

November 11, 2010
By Charles Q. Choi

The Mars Phoenix mission dug into the soil of Mars to see what might be hidden just beneath the surface. Samples from this trench were delivered to the Wet Chemistry Laboratory, which was part of Phoenix's Microscopy, Electrochemistry, and Conductivity Analyzer (MECA). Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

The first and only attempts to search for life on Mars were the Viking missions launched in 1975. Now scientists are suggesting the next decade of robotic probes sent to the red planet should make the search for life the highest priority.

After the Viking missions, the general consensus was that cold, radiation, hyper-aridity and other environmental factors ruled out the chances for microbial activity on or near the surface of Mars. This assumption -- based largely on how Vikings instruments did not detect organic compounds that would have indicated martian life  has been reinforced by each follow-up mission since then.

The Mars Science Laboratory, scheduled for launch in 2011, is dedicated to searching for evidence that the martian environment was once capable of supporting life on the red planet. However, some scientists argue the strategy for Mars exploration should center on the search for life itself -- extant life that is either active today or is dormant but still alive.

"There is no human task more significant and profound than testing if we are alone or not in the universe, and Mars must be the first place to look, as it is just facing our front yard," said astrobiologist Alberto Fairen at the SETI Institute and NASA Ames Research Center. "Finding life on Mars would be the most important scientific achievement of this century."

The Viking landers had detected organic molecules such as methyl chloride and dichloromethane, but these had been dismissed as terrestrial contamination  namely, cleaning fluids used to prepare the spacecraft when it was still on Earth.

The Phoenix lander spotted magnesium perchlorate in the soils, which can destroy organic residues. This discovery has caused scientists to rethink the Viking assumptions. Because Viking heated its samples, it could have caused a chemical reaction between perchlorate and any organics present, thereby destroying the organics.

The recent detection of methane on Mars has also revived the possibility of past or even extant life just below the surface, since life is one of the primary producers of methane on Earth.

As hostile as Mars might be for life, numerous examples exist of life surviving in extreme environments on Earth. For instance, microbes are seen in cold, dry soils of the Antarctic Dry Valleys. These soils are arranged into a layer of dry permafrost overlying ground ice, a structure similar to some soils on Mars. Debris-rich ice layers in glaciers trap water films and mineral dust that can serve as a basis for life on Earth, and similar layers are seen at Mars' northern polar deposits.

Microbes even live in salt knobs in the hyper-arid Atacama Desert in Chile, which is often described as similar to martian soils.

A number of studies suggest the lowlands of Mars's northern hemisphere were once covered in water. A possible shoreline near the giant volcano Olympus Mons was photographed in detail by the Viking spacecraft and by the Mars Orbiter Camera. Credit: NASA

These analogs of Mars on Earth suggest there are relatively few areas on Mars that could support life: ice-cemented ground, massive ice deposits and certain porous salts.

"Probes have been sent to regions of Mars where ice-cemented ground is common  this was the case of Phoenix, in the northern plains," Fairen said. "Other environments, such as hundreds of regional accumulations of chloride salts, have been discovered very recently, only three years ago, and are dispersed on the ancient southern highlands. In any case, there have been no attempts to analyze any of these environments with modern biological instruments to search for life, extant or extinct."

Fairen and his colleagues recommend a new strategy for the next decade of robotic investigations on Mars, one in which the search for extant life is the first priority.

Comparison of Mars Science Laboratory and Mars Exploration Rover. The Mini Cooper-sized MSL rover is twice as long (about 2.8 meters, or 9 feet) and four times as heavy as the Spirit and Opportunity rovers. Credit: NASA

"We call for a long-term architecture of the Mars Exploration Program that is organized around three main goals in the following order of priority  the search for extant life, the search for past life, and sample return," Fairen said.

The researchers envision probes targeting the kinds of areas where life might be found, and carrying instruments that can provide indisputable evidence  such as actual microbes -- for the presence or absence of life. Robotic missions in search of spores, dormant life or organic remains could, for instance, drill a few yards down to reach ice-rich layers shielded from the high levels of radiation at the surface and use microscopes to examine their finds.

A mission aimed at looking for extant life would also be ideal for finding any extinct life, since dead organisms likely would be found in the same places as live ones would. Since soil bacteria in the Atacama Desert are spread out in a patchy manner, any new missions to search for life on Mars should incorporate a rover. Landers should also be used to return samples, if at all possible.

"The technology is ready," Fairen said. "We only need a new impulse and more ambition."

Mars gets as far as 250 million miles away, but many parts of it closely resemble places on Earth, including its landscape, history of water, soil and even its weather, says a Texas A&M University researcher in the current ...

(PhysOrg.com) -- Experiments prompted by a 2008 surprise from NASA's Phoenix Mars Lander suggest that soil examined by NASA's Viking Mars landers in 1976 may have contained carbon-based chemical building blocks of life.

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11 comments

The big philosophical problem with looking for life on Mars is what to do if you find it?

The first issue that comes to mind is that finding life on another world, even one as close to Earth as mars, has a big impact on the view that humanity and Earth in general has a privileged place in the universe. If life is common why should a deity give mankind a privileged position?

Then there is the question of what to do with Mars if life is found? By all appearances any ecosystem is likely to be fragile and, as the only example of extraterrestrial life of immense value. Any threat to that ecosystem should be VERY carefully thought through. In some novels I have read a moratorium is put on landing on worlds where life is found (Stephen Baxter, Manifold Space), in others it's "we come in peace but shoot to kill" (Star Trek).

Personally I would be very pleased if life on another world was proven in my lifetime. The answer to the age old question "are we alone?" is then "probably not?".

It's not the discovery of past or present life on Mars that will be the world-shaker, it's the possibility that the SAME life forms existed on Mars as on the Earth, either now or in the distant past.

The implications of this would go far beyond the mere confirmation of life on other worlds, it would indicate involvement of highly advanced intelligences with our worlds long ago. The only way you would get the same species of larger life forms on both Earth and Mars at the same time would be transplantation by intelligent device.

Arkaleus jumps from "same life forms" to "same ... larger life forms". It's quite possible that life started on Mars and was transported to Earth (or vice versa). Finding bacteria-level life forms with a genetic code similar to that of all Earth life would be a sign of that.

On the other hand, if the life is truly alien, then that implies a second abiogenesis, which would be an even more remarkable find.

The implications of this would go far beyond the mere confirmation of life on other worlds, it would indicate involvement of highly advanced intelligences with our worlds long ago. The only way you would get the same species of larger life forms on both Earth and Mars at the same time would be transplantation by intelligent device.

Thats not the only way life could be transported between nearby worlds. IF a large asteroid impacted mars and ejected rocks which contained life forms they could land on earth and potentially tranport the life forms here (or vice versa). Its called Panspermia or Exogenesis (related but distinct theories) and was actually first proposed in the 5th Centruy BC by a greek philosopher called Anaxagoras. So not a new idea at all!

The first issue that comes to mind is that finding life on another world, even one as close to Earth as mars, has a big impact on the view that humanity and Earth in general has a privileged place in the universe.

Does any rational person think that anymore? That notion was discredited centuries ago.

If life is common why should a deity give mankind a privileged position?

The question is faulty because it presupposes the existence of a deity. Whether life is common or not should have no bearing on the presumptive existence of metaphysical beings.

The question is faulty because it presupposes the existence of a deity. Whether life is common or not should have no bearing on the presumptive existence of metaphysical beings.

I agree with you on the original grounds, however just because we live in a scientific universe doesn't mean there aren't deities.

Even if there is no progenitor deity for the entire universe, "Any sufficiently advanced Technology is Indistinguishable from Magic". It is possible that billions of species have mastered physics to such an extent that each of them becomes the deity of a new universe, perhaps with or without new/different physics and/or afterlifes or lack thereof.

If there are billions of sentient species in the universe, it is only logical that at least some evolve to a deity stage if such an evolution is possible.

I'm fairly optimistic about the possibility of finding bacterial life (or the remnants of life) on Mars or maybe Europa. However, sentient, spacefaring beings, in my opinion,will probably be incredibly rare ( maybe 1 per galaxy at any time).

How then will you explain identical larger life forms between the worlds?

Necessary path of evolution?

It seems that some features on animals on earth have evolved independently, yet reached the same structure. I wouldn't put it too improbable that some sort of critter had developed on mars that was, within reason, exactly the same as you can find here.

If you found the remains of a gray squirrel on mars, that would require some explaination.

Do you observe "evolution" producing identical species in two regions? Are you trying to claim that evolution into certain forms is inevitable and deterministic? If so, you are making claims that are not supported by most biologists. Parallel evolution is NOT the rule, VARIATION is the rule.

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